1. Field of Invention
The invention relates generally to a headlight for a motor vehicle and, more specifically, to a headlight for a motor vehicle having an interchangeable complex light source.
2. Description of Related Art
The present invention relates to a headlight for a motor vehicle with a housing, at least one semiconductor light source generating light for a main function of the headlight, a cooling body touching the semiconductor light source in thermal coupling, an optical system collecting and directing light of the semiconductor source, a securing frame mechanically connected to the housing which holds the semiconductor light source with the cooling body and the optical system in the housing, and having an interface between a first part forming a complex light source and includes at least the semiconductor light source and the cooling body, and a second part, including at least the holder, wherein the first part is connected to the second part at the interface so that it can be separated without destruction. Such a headlight is known from published U.S. Pat. No. 7,712,948.
In the art of illuminating devices for motor vehicles a distinction is made between “lights” and “headlights.” Lights serve the purpose of signaling the presence and/or behavior of a motor vehicle and/or the intentions of its driver to other traffic participants. For example, brake lights, flashing lights, and navigation lights (without this being an exhaustive list).
Headlights serve the purpose of actively lighting the roadway in front of a motor vehicle such that the driver can quickly recognize obstacles in the roadway. The light distributions generated by headlights needs to be compliant with government regulations (for example, to prevent the blinding of other traffic participants). Examples of light distributions generated by headlights include passing light and high beam light distributions (without this being an exhaustive list).
The task or capacity of a component to generate light distributions, be it light distributions or headlight distributions, is also referred to in the art as a light function. With respect to an illuminating device acting mainly as a headlight, headlight functions are also referred to as the “main function: so as to distinguish from other light functions provided by the same illuminating device (for example, when an illuminating device also performs signal light functions).
As known in the art of mass-produced road vehicles, semiconductor light sources have only been used for main headlight functions since around the year 2008, and were introduced earlier for signal light functions. One reason for the delay was the need for higher electric power for main functions in comparison to signal functions.
Because of the relatively lower light fluxes produced by semiconductor light sources used in the automotive industry, several semiconductor light sources are typically combined into complex light sources for main headlight functions, so as to obtain the desired overall high light fluxes. Because of the long service life of light emitting semiconductors, little emphasis has been placed on repair options for headlights with semiconductor light sources until recently. Further, at the beginning of the development of high-performance semiconductor light sources, little data was available about the service life and the probability of failure of the light sources. Initially, it was assumed that the service life of the semiconductor light sources would be more than sufficient for the service life of a motor vehicle. However, there is now great deal more experience available about the durability and the probability of failure of semiconductor light sources used for main headlight functions. There is a desire in the art for interchangeable semiconductor light sources. Particularly in the case of motor vehicles from the mid-range or lower-range price segment, high repair costs for used motor vehicles are undesirable, even where there is a high probability that few motor vehicles are affected by light source failures. Without interchangeable semiconductor light sources, the entire headlight assembly would have to be replaced, which could require a disproportionately high cost compared to the value of the vehicle.
However, difficulties arise in the case of such a replacement. Unlike halogen lamps, semiconductor light sources (such as LEDs) have a thermal interface in addition to the usual electrical and mechanical interfaces (for a power supply and positioning the light source). The thermal interface conducts away the heat generated in the operation of the semiconductor light source. Typically, the LED is firmly thermally coupled to a cooling body with thermal adhesives or heat sink paste. Thus, unlike the mechanical and electrical interfaces, it is difficult to provide the LED with a separable connection.
Further, in the event of a change of the light source there is the danger of the optical system going out of adjustment and causing the oncoming traffic to be blinded. Moreover, light modules for main headlight functions typically require a horizontal and a vertical default setting. Because of this, mounting light modules is expensive and typically prevents disassembly and replacement of the light modules for repair purposes. For this reason, light modules known in the art involve fixed units, where the light module can not be changed without destroying the unit after installation of the headlight during production.
To change LED light sources in the headlight in spite of these obstacles, Published U.S. Pat. No. 7,712,948 provides a light source module that has at least one light emitting element (in particular, LEDs), fiber optics, and collimating elements or lens elements. In addition, a retainer for such a system is provided, in particular in the form of a motor vehicle headlight. The headlight also has an optical system. The light source module is equipped to be positioned on a reference plane of the optical system, wherein it is also equipped to be replaced in a simple way, in particular without requiring soldered or welded connections.
The light source module known in the art has light exit surfaces arranged in series. A longitudinal edge of this arrangement is considered an optical element and should be reproduced by a further optical element (referred to as secondary as a light/dark border of a light distribution of the headlight. To this end, an exact and stable positioning of the longitudinal edge is necessary with respect to the further optical element. First, second, and third reference points are provided for this exact positioning between optical faces of the module and the optical system of the headlight. For example, the reference points should be made of hard rubber, plastic or metal. Position correction should be made possible by altering the thickness of the reference points. A change in the position of the LEDs with their cooling body relative to the remaining light module is also mentioned as an alternate setting option.